I am such a fan of Rhys Bowen, especially her Royal Spyness series. Her amateur sleuth, Georgie heads off to Transylvania to represent the British at a wedding to unite the Bulgarian and Romanian royal houses in Royal Blood.

This one has romance, a castle with secret passages, and murder/mayhem. And you can't have a castle in Transylvania with out the hint of vampires and werewolves. Plus, I learned about oubliettes (small dungeons with hidden entrances).

Royal Blood is a fun read. I'm looking forward to seeing how the characters evolve in the series.